Signal processing circuit for a hall sensor and signal processing method

ABSTRACT

Signal processing circuit for a Hall sensor and signal processing method. Signal processing circuits for four-phase spinning Hall magnetic field sensors, corresponding methods and corresponding magnetic field sensor apparatuses are provided. In this case, a correction signal (c) is generated on the basis of a first feedback signal (fb1) and a second feedback signal (fb2), wherein the first feedback signal (fb1) is provided with a shorter signal propagation time than the second feedback signal (fb2).

FIELD

The present application relates to signal processing circuits and tosignal processing methods for Hall sensors and to magnetic field sensorapparatuses having such Hall sensors and signal processing circuits.

BACKGROUND

Magnetic field sensor apparatuses for measuring a magnetic field areused in a multiplicity of applications, for example for detectingmovements. In such applications, a movement of an element causes achange in a magnetic field which is then captured by a magnetic fieldsensor apparatus.

Hall sensors are one type of magnetic field sensors which are used insuch magnetic field sensor apparatuses. In some implementations, Hallsensors have four connections, wherein a bias current is applied to twoconnections and a Hall voltage is tapped off at the two otherconnections, the magnitude of which voltage depends on a magnetic fieldcomponent perpendicular to a plane of the Hall sensor.

In order to reduce an offset, such Hall sensors are operated in someimplementations using a so-called spinning current technique. In thistechnique, the connections which are used to apply the bias current andto tap off the Hall voltage change in different operating phases, and anoffset can then be computationally removed and therefore reduced bycombining the voltages tapped off in different operating phases. In thiscase, two-phase spinning schemes and four-phase spinning schemes areused, in which case four-phase schemes generally provide a betterreduction in the offset. Such techniques are often combined withchopping at a frequency corresponding to the changing of the phases.

In this case, filtering is necessary in order to eliminate or at leastreduce ripple in the output signal at the frequency of the spinningcurrent (that is to say the frequency at which the operating phaseschange).

A conventional technique for this is to use a two-phase feedback loop,which may be insufficient, however, at high frequencies, for exampleabove 250 kHz.

In a conventional solution for such high frequencies, parallel notchfilter stages are used in a signal path which is coupled to a Hallsensor. In this solution, sampling effects may occur in the outputsignal if the magnetic field changes quickly and an input signal of thesignal path therefore has a step.

SUMMARY

A signal processing circuit as claimed in claim 1 and a method asclaimed in claim 13 are provided. The subclaims define furtherembodiments.

One or more embodiments provides a signal processing circuit including:

a combiner for receiving an output signal from a four-phase spinningcurrent Hall sensor and a correction signal and for combining the outputsignal and the correction signal to form a corrected signal,

a main signal path which is configured to receive the corrected signaland to output an output signal,

a second signal path which branches off from a node within the mainsignal path and is configured to provide a first feedback signal,wherein the second signal path has a shorter signal propagation timethan the main signal path, and

a processing device which is configured to generate the correctionsignal for reducing ripple in the output signal on the basis of thefirst feedback signal and the output signal as a second feedback signal.

One or more embodiments provides a signal processing method including:

providing a second feedback signal from an output of a main signal pathwhich is coupled to a four-phase spinning current Hall sensor,

providing a first feedback signal which is diverted from a node withinthe main signal path, wherein the first feedback signal is provided witha shorter signal propagation time than the second feedback signal, and

generating a correction signal for an output signal from the Hall sensoron the basis of the first feedback signal and the second feedbacksignal.

The above summary is used merely as a brief overview of some embodimentsand should not be interpreted as being restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a magnetic field sensor apparatus accordingto one example embodiment.

FIGS. 2A and 2B show diagrams for illustrating spinning currenttechniques.

FIG. 3 shows a block diagram of a magnetic field sensor apparatusaccording to one example embodiment.

FIG. 4 shows example signals in the magnetic field sensor apparatus inFIG. 3.

FIG. 5 shows a circuit diagram of a magnetic field sensor apparatusaccording to one example embodiment.

FIG. 6 shows a flowchart for illustrating methods according to someexample embodiments.

FIG. 7 is a diagram for illustrating multiplexing, as is used in someexample embodiments.

DETAILED DESCRIPTION

Various example embodiments are explained in detail below with referenceto the accompanying drawings. These example embodiments are used merelyfor explanation and should not be interpreted as being restrictive. Inother example embodiments, some of the illustrated features (components,elements, operations and the like) may thus be omitted and/or replacedwith alternative features or components. In addition to the explicitlyillustrated and described features, further features, for examplefeatures conventionally used in magnetic field sensor apparatuses, canbe provided.

Features of different example embodiments may be combined with oneanother, unless stated otherwise. For example, some variations,modifications and alternatives are described only in relation to oneexample embodiment in order to avoid repetitions, but may also beapplied to other example embodiments.

Connections or couplings which are described below relate to electricalconnections or couplings, unless stated otherwise. Such electricalconnections or couplings can be modified, for example by providingadditional elements or by omitting elements, as long as the fundamentalfunction of the electrical connection or coupling, for example thetransmission of a signal, the transmission of an item of information,the provision of a voltage or the provision of a current, is notsubstantially changed.

FIG. 1 shows a magnetic field sensor apparatus according to one exampleembodiment which comprises a signal processing circuit according to oneexample embodiment.

As a magnetic field sensor, the magnetic field sensor apparatus in FIG.1 has a Hall sensor 10. The Hall sensor 10 is operated using a spinningcurrent technique and, in implementations, using a four-phase spinningcurrent technique, as was briefly mentioned in the introductory part ofthe description and will also be explained in yet more detail furtherbelow with reference to FIGS. 2A and 2B. The circuit components used forthis purpose, such as switches for optionally applying a bias current todifferent connections, corresponding current or voltage sources andswitches for optionally tapping off the Hall voltage at differentconnections, can be implemented in any conventional manner and aretherefore not explicitly illustrated.

An output signal so from the Hall sensor 10, that is to say the Hallvoltage which has been tapped off or a signal derived therefrom, issupplied to a first input of an adder 11. A correction signal c, thegeneration of which is described in more detail below and which is usedto filter out, that is to say eliminate or at least reduce, ripple, issupplied to a second input of the adder 11. In this case, the term“adder” should generally be understood as meaning an element whichcombines two signals and can also subtract (depending on the signconvention used) the signals, for example, and can also be generallyreferred to as a combiner.

An output signal k corrected in this manner from the adder 11 issupplied to a main signal path having a first amplifier stage 12followed by a second amplifier stage 13. An output signal o can betapped off at an output of the second amplifier stage 13. It should benoted that the main signal path may also have yet further interposedelements, as indicated by the dashed line between the amplifiers 12 and13. The amplifier stages 12 and 13 are also used merely as examples ofpossible elements in a signal path, and other components are alsopossible, as will also be explained below on the basis of examples.

In order to form the correction signal c, a first feedback signal fb1 istapped off within the main signal path between the amplifier 12 and theamplifier 13 and a second feedback signal fb2 corresponding to theoutput signal o is tapped off at the output of the main signal path. Thefirst feedback signal fb1 and the second feedback signal fb2 aresupplied to a processing means 14. The processing means 14 may comprisea digital processing means, for which the feedback signals fb1, fb2 aredigitized. The digitization can be carried out using a track-and-holdcircuit or a sample-and-hold circuit followed by an analog/digitalconverter, in which case a single circuit of this type can also be usedfor both feedback signals fb1, fb2 by means of a multiplexer. Examplesof this are explained in yet more detail later. A 1-bit digital/analogconverter can be used as the digital/analog converter. Such a digitalprocessing means can be implemented by means of any components whichenable the analog/digital conversion of the signals fb1, fb2, thedigital processing of the signals converted in this manner and thedigital/analog conversion of the result in order to form the correctionsignal c. For example, 1-bit or multi-bit analog/digital anddigital/analog converters, signal processors, logic circuits, counters,multi-purpose processors and the like can be used.

In the case of a four-phase spinning current technique, the firstfeedback signal fb1 can be combined from two successive phases, whereasthe second feedback signal fb2 is combined over all four phases in orderto form the correction signal c.

Since the feedback signal fb1 is tapped off within the main signal path,faster feedback is possible here than with the signal fb2, which, insome example embodiments, in particular at high frequencies, can resultin a better reduction in ripple than in the case of simple feedback fromthe output of the main signal path. A simple implementation can beenabled by the digital processing. The digital processing can be carriedout by simply incrementing and decrementing the correction signal on thebasis of the feedback signals fb1, fb2 digitized by means of a 1-bitconversion. Examples of this are likewise explained in yet more detaillater. The correction signal c can then be generated by means ofdigital/analog conversion at the output of the processing means 14.

Before the approaches with two feedback signals and digital processingwhich are explained with reference to FIG. 1 are explained in moredetail on the basis of FIGS. 3 to 5, the spinning current techniques, asis used in various example embodiments, shall now be explained in moredetail with reference to FIGS. 2A and 2B.

In this case, FIG. 2A shows a two-phase spinning current technique,whereas FIG. 2B shows a four-phase spinning current technique.

It should be noted that the signals illustrated in FIG. 2 and signalsillustrated in other figures are used merely for illustration, andactual signal profiles may depend on the exact implementation and alsoon an applied magnetic field which is measured by the Hall sensor.

A Hall sensor 20 is schematically illustrated in two phases in FIG. 2Aand is denoted using the reference sign 20A or 20B, wherein the phasesare also denoted using PH1 and PH2. In this case, the Hall sensor isillustrated as a square, wherein a first current is impressed at twocorners of the opposite square and the Hall voltage is then tapped offat the other two opposite corners. Dashed arrows for the Hall sensors20A, 20B show the direction of the bias current in the two phases PH1,PH2.

A curve 21 shows an example of a resulting signal, and a curve 22 showsthe offset. A processing signal C can be used to smooth the signal, asillustrated in a curve 23, in order to eliminate ripple, whereas theoffset remains low, as represented by a curve 24.

FIG. 2B shows a four-phase spinning current technique. In this case, aHall sensor in four phases PH1-PH4 is identified using the referencesigns 25A to 25D, in which case dashed arrows again indicate thedirection of the bias current. Whereas the bias current is impressed intwo directions which are perpendicular to one another in FIG. 2A, thebias current is also impressed with two different polarities for eachdirection (illustrated as vertical and horizontal in FIGS. 2A and 2B) inFIG. 2B, which results in a total of four phases.

A resulting signal is illustrated in a curve 26, in which case an offsetis reduced to a greater extent here, as illustrated by a curve 27, thanin the curve 22 in FIG. 2A. The correction signal c can again be usedhere to smooth the signal, as illustrated by a curve 28, that is to saythe ripple can be eliminated or at least reduced, whereas the offsetremains low, as illustrated by a curve 29.

If the Hall voltages in the phases 25A, 25B, 25C and 25D are denotedusing V1, V2, V3 and V4, the following applies to the Hall voltageV_(Hall) which is caused by the magnetic field:

VHall=V1−Vos1−Vos3   (1)

VHall=V2+Vos1−Vos3   (2)

VHall=V3−Vos2+Vos3   (3)

VHall=V4+Vos2+Vos3   (4)

In this case, Vos1, Vos2 are offsets which stem from differentresistances in the two opposite directions of two successive phases ineach case, whereas Vos3 is a component which stems from the anisotropyof the sensor (different behavior in the phases 25A, 25C and differentbehavior in the phases 25B, 25D).

The offsets Vos1 to Vos3 can be calculated from the equations asfollows:

Vos1=(V1−V2)/2   (5)

Vos2=(V3−V4)/2   (6)

Vos3=(V1+V2−V3−V4)/4   (7)

As is clear, the actual Hall voltage V_(Hall) and therefore the measuredmagnetic field freed from the offsets Vos1-Vos3 can then be determinedfrom each of the voltages V1 to V4 by means of equations 1 to 4.

In example embodiments, the slower feedback signal fb2 is used tocalculate the offset Vos3, whereas the feedback signal fb1 is used tocalculate the offsets Vos1 and Vos2.

The correction signal c can then be determined by combining the offsetsin each phase according to equations 1 to 4.

FIG. 3 shows a block diagram of a magnetic field sensor apparatus havinga signal processing circuit according to a further example embodiment.

The example embodiment in FIG. 3 comprises a Hall sensor 30 having adownstream signal processing circuit. As already described for the Hallsensor 10 in FIG. 1, the Hall sensor 30 is operated using a spinningcurrent scheme and is operated using a four-phase spinning currentscheme in the example embodiment in FIG. 3.

The Hall sensor 30 outputs a Hall voltage so to an adder 314 whichcorresponds to the adder 11 in FIG. 1.

The adder 314 also receives a correction signal c and combines thelatter with the signal so to form a corrected signal k. In the examplein FIG. 3, the signals so, c and k are each voltage signals. Whereas thesignals are denoted using individual arrows, they may also bedifferential signals. The signal so may thus be a differential Hallvoltage which, as explained with reference to FIG. 2, is tapped off attwo opposite points, for example corners, of the Hall sensor 30.

The signal k is supplied to a main signal path 31 which then outputs anoutput signal o corresponding to the signal o in FIG. 1. The main signalpath 31 comprises a voltage/current (V/I) converter 32, one or moreprocessing devices 33 which operate in the current range, that is to sayuse the current signal used by the current/voltage converter 32, and acurrent/voltage converter 34 which converts the current signal output bythe processing device 33 into the voltage signal o.

In one example embodiment, the voltage/current converter 32 maycomprise, for example, a transconductance amplifier or a plurality oftransconductance amplifiers. The voltage/current converter 32 has asignal propagation time t_(d1). The processing device 33 may compriseone or more current mirrors, for example. The processing device 33 has asignal propagation time t_(d2). The current/voltage converter 34 may beimplemented as a transimpedance amplifier, for example, and has a signalpropagation time t_(d3), with the result that a total signal propagationtime, also referred to as latency, of the main signal path ist_(d1)+t_(d2)+t_(d3).

However, the components 32, 33 and 34 are only one example and othercomponents, for example components operating in the voltage range, canalso be used in other example embodiments.

The signal is tapped off between the voltage/current converter 32 andthe processing device 33 and is supplied to a current/voltage converter35 which provides a second signal path 311 for providing a firstfeedback signal fb1 having a shorter signal propagation time. Thecurrent/voltage converter 35 may likewise be configured as atransimpedance amplifier and has a signal propagation time t_(d4). Inthis case, t_(d4) is considerably lower than the sum of t_(d2) andt_(d3), for example at least by a factor of 2, at least by a factor of 3or at least by a factor of 5. The second signal path 311 can also bereferred to as a replica path for the main signal path 31 and has asimilar behavior in a certain manner (for example it likewise in turnoutputs a voltage signal), but has a shorter signal propagation time. Inthe example in FIG. 3, the processing device 33 has been omitted, forexample, whereas the current/voltage converter 35 can be constructed ina manner corresponding to the current/voltage converter 34, but may alsobe a simpler current/voltage converter having a shorter signalpropagation time. The signal at the outputs of the current/voltageconverters 34, 35 can be respectively chopped at a chopper frequencytchop corresponding to the frequency of the spinning current method.This is indicated by choppers 312, 313 in FIG. 3.

The output signal from the second signal path 311 is supplied, as thefirst feedback signal fb1, to a multiplexer 36 having a track-and-holddevice 37 (T&H) connected downstream. The track-and-hold device 37operates at the same frequency as the spinning current technique, andthe multiplexer 36 changes over between the signal fb1 and the signalfb2, for example after each run through all four phases. In this case,the signal fb1 is used to ultimately compensate for two-phase ripple(caused by the opposite directions of the current, see FIGS. 2A and 2B),whereas the feedback signal fb2 is used to compensate for the ripplewhich is additionally caused by the directions of the bias current whichare perpendicular to one another.

The output signal from the track-and-hold device 37 is digitized by ananalog/digital converter 38, a 1-bit quantizer in the example in FIG. 3,and is processed further by a digital signal processor. The 1-bitquantizer can operate substantially as a comparator which compares itsinput signals with a threshold value and indicates a 0 or 1 depending onthe comparison. If differential input signals are used for thecomparator, the threshold value can be selected to be differential 0 V(that is to say a voltage difference of 0 between the differential inputsignals). In the case of a single-pole signal with respect to areference potential, a threshold value corresponding to 0 V for adifferential signal can be selected. In this case, the digital signalprocessor 39 calculates a digital version of the correction signal cfrom the samples. As explained later with reference to FIG. 5, thedigital signal processor 39 may comprise counters. However, more complexcalculations are also possible. The basis in this case is equations (1)to (4) which were explained above with reference to FIG. 2B and fromwhich the useful signal and the offset can be calculated and from whichthe offset can therefore be compensated for.

The output signal from the digital signal processor 39 is then subjectedto digital/analog conversion by a digital/analog converter 310 in orderto form the correction signal c.

For further explanation, FIG. 4 shows examples of the signals so, c andk in FIG. 3. In this case, a curve 40 shows an example of the signal sooutput by the Hall sensor 30.

A curve 41 shows an example of the profile of a corresponding correctionsignal c which is substantially inverse to the ripple in the curve 40. Acurve 42 shows a corresponding example of the corrected signal k inwhich the ripple is suppressed.

FIG. 5 shows a circuit diagram of a magnetic field sensor apparatushaving a signal processing circuit according to a further exampleembodiment. The magnetic field sensor apparatus in FIG. 5 comprises aHall sensor 50 which is operated using a four-phase spinning currenttechnique and outputs a Hall voltage so. The Hall voltage so is suppliedto an adder 51, the function of which corresponds to the adders 11 inFIG. 1 and 311 in FIG. 3. The adder 51 combines the signal so with acorrection signal c in order to output a corrected signal k.

The corrected signal k is supplied to a transconductance amplifier 52which converts it into a current signal. This current signal is suppliedto a first transistor 55 in a sequence of first current mirrors 53, ncurrent mirrors in FIG. 5, which are an example of a processing devicein the current range.

An output of the n first current mirrors 53 is connected to an input ofa transimpedance amplifier 54 which generates the output signal o as avoltage signal and also outputs a second feedback signal fb2corresponding to the output signal o.

Furthermore, the transistor 55 is used as a first transistor in asequence of second current mirrors 56, wherein m second current mirrors56 are provided here. In this case, m is less than n in some exampleembodiments in order to provide a second signal path having a shortersignal propagation time. An output of the second current mirrors 56 issupplied to a current/voltage converter 57 which, in the example in FIG.5, is formed substantially by a resistor which is connected to acommon-mode voltage Vcm. The output current of the second currentmirrors 56 causes a voltage drop across the resistor and therefore acurrent/voltage conversion. This current/voltage converter 57 may have ashorter signal propagation time than the transimpedance amplifier 54.Overall, in the example embodiment in FIG. 5, a main signal path throughthe first current mirrors 53 and the transimpedance amplifier 54, whichoutputs the second feedback signal fb2, has a greater signal propagationtime than the signal path through the second current mirrors 56 and thecurrent/voltage converter 57 which outputs a first feedback signal fb1.

The feedback signals fb1 and fb2 are supplied to a multiplexingtrack-and-hold device 59, the function of which corresponds to themultiplexer 56 and the track-and-hold device in FIG. 3. The signaloutput by the device 59 is digitized by an analog/digital converter 510,for example a 1-bit quantizer, and is supplied to a digital processingdevice which can be implemented, for example, by means of a digitalsignal processor such as the digital signal processor 39 in FIG. 3.

The digital signal is multiplexed using a multiplexer function 511 andis divided in this case into the samples corresponding to the digitizedfeedback signal fb1 and samples corresponding to the digital feedbacksignal fb2. The samples which correspond to the second feedback signalfb2 control a four-phase counter 513 which counts up or down dependingon a comparison of the samples with a threshold value which maycorrespond to a mean value. The direction of counting up or down can beselected on the basis of the sampling phase, with the result that Vos3is substantially calculated according to equation (7). In a similarmanner, the samples which correspond to the first feedback signal fb1are supplied to a two-phase counter 512 which substantially calculatesVos1 and/or Vos2 according to equations (5) and (6) by counting up anddown. The outputs from the counters 512, 513 are added using an additionfunction 514 and are converted into the analog correction signal c bymeans of a digital/analog converter 515. In this case, in oneimplementation, the counters 512, 513 generate a differential 0 signalin a center position of a control range of the feedback signals fb1,fb2, with the result that the center position does not contributeanything to the correction signal c. Furthermore, the counters 512, 513generate +/− differential signals for compensating for the ripple, whichare then converted into corresponding components of the correctionsignal c by the digital/analog converter 515.

The function of the multiplexer 36 in FIG. 3 or of the multiplexing andtrack-and-hold device 59 in FIG. 5 is explained in yet more detail onthe basis of FIG. 7.

FIG. 7 shows the operation of the spinning Hall sensor in FIG. 2B over alonger period, wherein the reference signs 25A to 25D denote the Hallsensors in the corresponding phases PH1 to PH4 in FIG. 2B. For each runthrough all four phases, either the signal fb2 or the signal fb1 isforwarded. On the basis of the signal fb2 (fb2 multiplexed in FIG. 7), acalculation is carried out on the basis of all phases, for example thecalculation of Vos3 according to equation (7), whereas, on the basis ofthe signal fb1, calculations are carried out on the basis of two phases(PH1/PH2 multiplexed and PH3/PH4 multiplexed), for example according toequations (5) and (6). However, other multiplexing schemes are alsopossible. For example, the multiplexer can be reorganized during eachphase, with the result that both feedback signals fb1, fb2 arecontinuously evaluated. The diagram in FIG. 7 is therefore used only forillustration. Since fb2 is evaluated together over all phases, thiscorresponds to an evaluation at the chopper frequency.

It should be noted that the calculation of the correction signal c bymeans of counters is only one example, and it is also possible to useother possibilities to calculate the correction signal c substantiallyon the basis of equations (5) to (7), for example approaches which useaccumulators.

FIG. 6 is a flowchart for illustrating a method according to someexample embodiments. The method in FIG. 6 can be carried out, forexample, using the magnetic field sensor apparatuses discussed withreference to FIGS. 1, 3 and 5, but can also be implemented in othermagnetic field sensor apparatuses. In order to simplify the description,the method in FIG. 6 is described with reference to the abovedescription of the apparatuses.

At 60, the method comprises provision of a second feedback signal froman output of a main signal path which is coupled to a Hall sensor,wherein the Hall sensor is operated using a spinning current method.This corresponds to the provision of the feedback signal fb2 in FIGS. 1,3 and 5.

At 61, the method comprises provision of a first feedback signal whichis diverted from an intermediate node of the main signal path (forexample from the node between the components 12 and 13 in FIG. 1, thecomponents 32 and 33 in FIG. 3 or from the transistor 55 in FIG. 5). Inexample embodiments, the first feedback signal (fb1) thereby has ashorter signal propagation time than the second feedback signal (fb2).

At 62, the method comprises processing of the first and second feedbacksignals, in particular digital processing, in order to form a correctionsignal (for example the correction signal c in FIGS. 1, 3 and 5). Inthis case, the processing can be carried out as described above on thebasis of equations (5) to (7), for example by means of counters asillustrated in FIG. 5. The other variants and modifications describedwith reference to FIGS. 1 to 5 can also be applied in a correspondingmanner to the method.

It should be noted that the first and second feedback signals can beprovided at 60 and 61 at substantially the same time, as shown in thevarious magnetic field sensor apparatuses, with the result that thesequence of the different operations which is illustrated in FIG. 6should not be interpreted as being restrictive here.

Some example embodiments are defined by the following examples:

Example 1. A signal processing circuit comprising:

a combiner for receiving an output signal from a four-phase spinningcurrent Hall sensor and a correction signal and for combining the outputsignal and the correction signal to form a corrected signal,

a main signal path which is configured to receive the corrected signaland to output an output signal,

a second signal path which branches off from a node within the mainsignal path and is configured to provide a first feedback signal,wherein the second signal path has a shorter signal propagation timethan the main signal path, and

a processing device which is configured to generate the correctionsignal for reducing ripple in the output signal on the basis of thefirst feedback signal and the output signal as a second feedback signal.

Example 2. The signal processing circuit according to example 1, whereinthe processing device comprises an analog/digital converter, a digitalcircuit for determining a digital version of the correction signal and adigital/analog converter for providing the correction signal from thedigital version of the correction signal.

Example 3. The signal processing circuit according to example 2, whereinthe processing circuit comprises a multiplexer device for receiving thefirst feedback signal and the second feedback signal and for optionallyforwarding the first feedback signal or the second feedback signal todownstream components of the processing device.

Example 4. The signal processing circuit according to example 3, whereinthe processing device comprises a track-and-hold device which isconnected downstream of the multiplexer device and the output of whichis coupled to an input of the digital/analog converter.

Example 5. The signal processing circuit according to one of examples 2to 4, wherein the digital circuit comprises a two-phase counter, whichdetermines a first component of the digital version of the correctionsignal on the basis of the first feedback signal, and a four-phasecounter, which is configured to determine a second component of thedigital version of the correction signal on the basis of the secondfeedback signal, and an addition component which is configured tocombine the first and second components.

Example 6. The signal processing circuit according to one of examples 1to 5, wherein the processing device is configured to determine a firstoffset component on the basis of the first feedback signal and todetermine a second offset component on the basis of the second feedbacksignal, wherein the correction signal is based on the first offsetcomponent and the second offset component.

Example 7. The signal processing circuit according to one of examples 1to 6, wherein the main signal path comprises a voltage/currentconverter, current range components connected downstream of thevoltage/current converter and a voltage/current converter, wherein thenode is between the voltage/current converter and the current/voltageconverter, and

wherein the second signal path comprises a further current/voltageconverter.

Example 8. The signal processing circuit according to example 7, whereinthe current range components comprise a first number of current mirrors.

Example 9. The signal processing circuit according to example 8, whereinthe second signal path comprises a second number of current mirrors.

Example 10. The signal processing circuit according to example 9,wherein the first number of current mirrors and the second number ofcurrent mirrors have a common input transistor.

Example 11. The signal processing circuit according to example 9 or 10,wherein the second number is lower than the first number.

Example 12. A magnetic field sensor apparatus comprising:

a signal processing circuit according to one of examples 1 to 11, and

the four-phase spinning current Hall sensor.

Example 13. A signal processing method comprising:

providing a second feedback signal at an output of a main signal pathwhich receives a four-phase spinning current Hall signal,

providing a first feedback signal which is diverted from a node withinthe main signal path, wherein the first feedback signal is provided witha shorter signal propagation time than the second feedback signal, and

generating a correction signal for the four-phase spinning current Hallsignal on the basis of the first feedback signal and the second feedbacksignal.

Example 14. The method according to example 13, wherein the correctionsignal is generated by means of at least partially digital processing.

Example 15. The method according to example claim 13 or 14, alsocomprising receiving the first feedback signal and

multiplexing in order to optionally forward the first feedback signal orthe second feedback signal to downstream processing.

Example 16. The method according to example 15, wherein the optionalforwarding is effected to a track-and-hold device with a downstreamanalog/digital converter.

Example 17. The method according to one of examples 13 to 16, whereinthe generation of the correction signal comprises a first countingoperation on the basis of the first feedback signal in order todetermine a first component and a second counting operation on the basisof the second feedback signal in order to determine a second componentand an operation of combining the first and second components.

Example 18. The method according to one of examples 13 to 17, whereinthe generation of the correction signal comprises determining a firstoffset component on the basis of the first feedback signal and a secondoffset component on the basis of the second feedback signal, wherein thecorrection signal is based on the first offset component and the secondoffset component.

Example 19. The method according to one of examples 13 to 18, whereinthe main signal path comprises a voltage/current converter, currentrange components connected downstream of the voltage/current converterand a voltage/current converter, wherein the node is between thevoltage/current converter and the current/voltage converter, and

wherein a second signal path for providing the first feedback signalcomprises a further current/voltage converter (35).

Example 20. The method according to one of examples 13 to 18, whereinthe provision of the second feedback signal comprises voltage/currentconversion in order to generate a current signal, processing of thecurrent signal in the current range in order to generate a processedcurrent signal, and current/voltage conversion of the processed currentsignal, and

the provision of the first feedback signal comprises furthercurrent/voltage conversion on the basis of the current signal.

Although specific example embodiments have been illustrated anddescribed in this description, persons with conventional expertknowledge will recognize that a multiplicity of alternative and/orequivalent implementations can be selected as a substitute for thespecific example embodiments which are shown and described in thisdescription without departing from the scope of the invention shown. Theintention is for this application to cover all adaptations or variationsof the specific example embodiments which are discussed here. Theintention is therefore for this invention to be restricted only by theclaims and the equivalents of the claims.

1. A signal processing circuit, comprising: a combiner configured toreceive an output signal from a four-phase spinning current Hall sensorand a correction signal, and combine the output signal and thecorrection signal to form a corrected signal; a main signal pathconfigured to receive the corrected signal and output an output signal;a second signal path that branches off from a node within the mainsignal path and is configured to provide a first feedback signal,wherein the second signal path has a shorter signal propagation timethan the main signal path; and a processing device configured togenerate the correction signal for reducing ripple in the output signalon the basis of the first feedback signal and the output signal as asecond feedback signal.
 2. The signal processing circuit as claimed inclaim 1, wherein the processing device comprises an analog/digitalconverter, a digital circuit configured to determine a digital versionof the correction signal, and a digital/analog converter configured toprovide the correction signal from the digital version of the correctionsignal.
 3. The signal processing circuit as claimed in claim 2, whereinthe processing circuit comprises a multiplexer device configured toreceive the first feedback signal and the second feedback signal andforward the first feedback signal or the second feedback signal todownstream components of the processing device.
 4. The signal processingcircuit as claimed in claim 3, wherein the processing device comprises atrack-and-hold device that is connected downstream of the multiplexerdevice, the track-and-hold device comprising an output that is coupledto an input of the digital/analog converter.
 5. The signal processingcircuit as claimed in claim 2, wherein the digital circuit comprises atwo-phase counter, which determines a first component of the digitalversion of the correction signal on the basis of the first feedbacksignal, and a four-phase counter, which is configured to determine asecond component of the digital version of the correction signal on thebasis of the second feedback signal, and an addition component which isconfigured to combine the first and the second components of the digitalversion of the correction signal.
 6. The signal processing circuit asclaimed in claim 1, wherein the processing device is configured todetermine a first offset component on the basis of the first feedbacksignal and to determine a second offset component on the basis of thesecond feedback signal, wherein the correction signal is based on thefirst offset component and the second offset component.
 7. The signalprocessing circuit as claimed in claim 1, wherein the main signal pathcomprises a voltage/current converter, current range componentsconnected downstream of the voltage/current converter, and acurrent/voltage converter, wherein the node is between thevoltage/current converter and the current/voltage converter, and whereinthe second signal path comprises a further current/voltage converter. 8.The signal processing circuit as claimed in claim 7, wherein the currentrange components comprise a first number of current mirrors.
 9. Thesignal processing circuit as claimed in claim 8, wherein the secondsignal path comprises a second number of current mirrors.
 10. The signalprocessing circuit as claimed in claim 9, wherein the first number ofcurrent mirrors and the second number of current mirrors have a commoninput transistor.
 11. The signal processing circuit as claimed in claim9, wherein the second number is lower than the first number.
 12. Amagnetic field sensor apparatus, comprising: a signal processingcircuit; and a four-phase spinning current Hall sensor, wherein thesignal processing circuit comprises: a combiner configured to receive anoutput signal from the four-phase spinning current Hall sensor and acorrection signal, and combine the output signal and the correctionsignal to form a corrected signal; a main signal path configured toreceive the corrected signal and output an output signal; a secondsignal path that branches off from a node within the main signal pathand is configured to provide a first feedback signal, wherein the secondsignal path has a shorter signal propagation time than the main signalpath; and a processing device configured to generate the correctionsignal for reducing ripple in the output signal on the basis of thefirst feedback signal and the output signal as a second feedback signal.13. A signal processing method, comprising: providing a second feedbacksignal at an output of a main signal path which receives a four-phasespinning current Hall signal; providing a first feedback signal which isdiverted from a node within the main signal path, wherein the firstfeedback signal is provided with a shorter signal propagation time thanthe second feedback signal; and generating a correction signal for thefour-phase spinning current Hall signal on the basis of the firstfeedback signal and the second feedback signal.
 14. The method asclaimed in claim 13, wherein the correction signal is generated by meansof at least partially digital processing.
 15. The method as claimed inclaim 13, further comprising: receiving the first feedback signal; andmultiplexing in order to forward the first feedback signal or the secondfeedback signal to downstream processing.
 16. The method as claimed inclaim 15, forwarding the first feedback signal and the second feedbacksignal via the multiplexing to a track-and-hold device with a downstreamanalog/digital converter.
 17. The method as claimed in claim 13, whereingenerating the correction signal comprises a first counting operation onthe basis of the first feedback signal in order to determine a firstcomponent of the correction signal, a second counting operation on thebasis of the second feedback signal in order to determine a secondcomponent of the correction signal, and a combining operation ofcombining the first and the second components of the correction signal.18. The method as claimed in claim 13, wherein generating the correctionsignal comprises determining a first offset component on the basis ofthe first feedback signal and a second offset component on the basis ofthe second feedback signal, wherein the correction signal is based onthe first offset component and the second offset component.
 19. Themethod as claimed in one of claim 13, wherein the main signal pathcomprises a voltage/current converter, current range componentsconnected downstream of the voltage/current converter, and acurrent/voltage converter, wherein the node is between thevoltage/current converter and the current/voltage converter, and whereina second signal path for providing the first feedback signal comprises afurther current/voltage converter.
 20. The method as claimed in claim13, wherein providing the second feedback signal comprisesvoltage/current conversion in order to generate a current signal,processing of the current signal in the current range in order togenerate a processed current signal, and current/voltage conversion ofthe processed current signal, and providing the first feedback signalcomprises a further current/voltage conversion on the basis of thecurrent signal.